LM7909

The LM7909 is a linear voltage regulator IC manufactured by National Semiconductor, now part of Texas Instruments. It is part of the LM79xx series of negative voltage regulators. Specifically, the LM7909 provides a fixed output voltage of -9 volts. It is designed to accept a wider range of input voltages than some other regulators and offers built-in thermal overload protection and short-circuit current limiting.

This regulator is a three-terminal device, typically housed in a TO-220 or TO-3 package. The three terminals are input, ground, and output. The input terminal receives the unregulated negative voltage, the ground terminal is connected to the common ground of the circuit, and the output terminal provides the regulated -9V. The LM7909 requires minimal external components, usually just a couple of capacitors for stability and filtering.

Applications for the LM7909 include power supplies for negative voltage rails in various electronic circuits, such as audio amplifiers, operational amplifier circuits, and general-purpose power regulation where a stable -9V supply is required. Its robustness and ease of use make it a common choice for designers needing a reliable negative voltage source. The device operates effectively within a specified range of input voltages, and its internal protection mechanisms help prevent damage under fault conditions.